A former South Korean national security adviser has been arrested on suspicion of covering up the case of a fisheries official killed by North Korean troops.
Suh Hoon denies destroying evidence that explained the fatal shooting of Lee Dae-jun at sea in 2020.
At the time it was reported he was killed trying to defect to North Korea over gambling debts and personal issues.
But prosecutors and his family say there is little evidence for this.
The case has sparked a political row. The current government accuses the previous government of seeking to curry favour with North Korea as it was attempting to improve ties.
Lee, a 47-year-old father of two, was on a patrol boat about 10km (6 miles) from the border with the North, near the island of Yeonpyeong, when he disappeared in September 2020, the South Korean defence ministry said at the time.
He had left his shoes behind on the boat and was found wearing a lifejacket by a North Korean patrol boat, Seoul claimed, stating that Lee was questioned before he was shot dead in the water a few hours later.
The tiny South Korean island watching the horizon
The South said North Korean troops then burned the corpse while at sea, adding that they believed this might have been an anti-coronavirus measure. Pyongyang did not comment on the incident.
The then government of President Moon Jae-in concluded Lee was killed while trying to defect, but this was reversed after his successor President Yoon Suk-yeol took office this year.
Mr Yoon's ruling People Power party said former President Moon and his aides "not only let Lee die but killed his honour by claiming his defection while treading on eggshells around (North Korean leader) Kim Jong Un's regime".
A previous inquiry by South Korea's Board of Audit and Inspection found that Mr Moon's government made no meaningful attempt to rescue Lee after learning he was drifting in waters near the Koreas' borders.
The Lee family also accused Mr Moon's government of not doing enough to save his life.
Mr Suh is suspected of ordering intelligence reports concerning Lee's killing be destroyed and manipulating evidence to support the claim of defection. He has accused the current administration of political retaliation.
For his part Mr Moon, whose efforts at improving relations with the North ended in failure, accuses the current government of making unfounded claims.